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T H E J O U R N A L O F I N D L ~ S l K I . 4 L .4ND E N G I N E E R I N G C H E M I S T R Y
768
solution of ammonium oxalate: determine lime bv titration with permanganate, or as desired. When much lead is present (more than j o per cent of the sample), boil a second time or evcn a third time with caustic soda. If the residue is well washed, no lead will remain with the lime. E X A ~ I P L E S - - ( I ) 0.5 g. of white lead and 0.j g. of whiting (CaO present, j 4 . 3 per cent) gave 54. 2 per cent CaO. ( 2 ) o . I g. of white lcsd and o. j g. of whiting (same amount of CaO as above) gave 5 4 . 2 per cent CaO, ( 3 ) 0 . 8 g. of white lead and o. 2 g. of whiting (CaO present, 10.8 per cent) gavc 1 0 . 3 per cent CaO. (4) 0 . 9 g. of white lead and 0 . I g. of whiting (CaO present, j.4 per cent) gavc j . 6 per cent CaO. C H X O M I U M I N MIXED P I G M E N T S
Much trouble is experienced in detecting sinall amounts 01 chromium in mixed pigments where chrome yellow has been used t o slightly modify an olive or drab shade of color. The following test is quickly and easily made, and gives good results Treat the pigment with a few cub of dilute nitric acid ( I : j ) , stir well, let stand a minute or two, filter, and t o the filtrate add a few cubic centimeters of hydrogen peroxide. A purple color indicates chromium, the chromic acid being oxidized t o perchromic acid by the hydrogen peroxide. The color is not permanent and soon fades out, especially with small amounts of chromium. This test shows the presence of a very minute quantity of chromium, and it works equally well with chrome green pig but for the reaction t o procecd successfully, t h mium must he present as chromic acid, and t h tion must not be heated. I~~IPRoYLn METHOD
Vol.
11,
No. 8
P R E P A R A T I O N O F STARCII I N D I C A T O R
Finally, I wish t o call attention t o a very convenient way of preparing starch indicator; which I devised several years ago. It depends on the wellknown fact t h a t starch is solubic in a dilute solution of salicylic acid. Indicator t h u s prepared keeps indefinitely; a sollition put away in a well-corked bottle in a dark cupboard and kept for z yrs. was found a t the end of t h a t time t o be unaltered and as good a s when first made up. uETlioo-.--Uissolae I g. of salicylic acid in 100 cc. of distilled water, boil, pour into i t I g. o i potato starch mixed with a little water, boil gently till starch has dissolved, let cool somewhat, and then dilute with cold distilled water t.o I liter. This solution is clear and transparent, and gives a fine, deep blue color with iodine.
A NEEDLE VALVE WITH DELICATE ADJUSTMENT FOR
HItiH PRESSURE GASES IlY s. w. Pnns nercivfd
m y23.
1919
Oxygen on t a p is an essentialfeaturc of every presentday laboratory hut thc ordinary valve lor opening a n d closing the steel cylinders is an unwieldy affair. Moreover, a standard connection interchangeable with all:
F O R CHROMIUX I N CHROME YELLOW
Dissolve 0 . j g. o i sample in 15 cc. of 2 0 per cent caustic soda, warming until dissolved, dilute t o about 200 cc. with cold water, add 2 g. of ferrous ammonium siiliate (previously dissolved in R little water), stir well, let stand a few minutes, acidulate strongly with dilute sulfuric acid, dilute cold t o nearly 400 cc., and titrate by permanganate. LXAMPLES-/I) o . j g. portions of chrome yellow used: titer of the permanganate was 10 mg. iron per cc. Found 2 9 . j per ccnt, 2 9 . 6 per cent, 2 9 . j per cent, 2 q . 6 per cent CrO,. Same sample tit.rated by potassium dichromate gave 2 9 . 6 per cent, 2 9 . j per cent CrOs. Same sample by the old standard method (treatment with ferrous ammonium sulfate) gave 2 8 . 9 per cent and 2 9 . 0 per cent CrOl. N s w M B T ~ ~OLD D Mniiw~ Per cent I'Ci cent 2................................ 26.8 26.3 3 ................................ 19.0 18.R 4 ................................ 28.8 28.4 5 ................................ 17.4 16.3
EXAaaFLB
This method is better than the old standard method using hydrochloric acid t o dissolve the chrome, as some chromes are partly insoluble in acid, h u t readily decomposed by the caustic soda as in Test j above.
cylinders by a ground metal joint was found t o he a! necessary feature in the designing of a calorimeter outfit of the oxygen bomb type. By slightly monify-~ ing the valve t h u s designed i t has been made avail;. able for service under all conditions. The essential' feature aside from the metal joint and lock-nut attachment is the possibility of definite control to the. extent t h a t by operation of the needle valve alone the gas may be taken directly from the cylinder to a corn-~
Aug., 1919
T H E JOURNAL OF IiVDUSTRIAL A N D ENGINEERING CHEMISTRY
bustinn train. Adjustment of t h e current of gas may easily be made t o t h e ordinary speed where t h e bubbles passing a n absorption bulb m a y readily be counted. T h e illustration shows t h e device as supplied for t h e purpose indicated. DEPARTMENT OF CHEMISTRY UNIVERSITY O F ILIJNOIS URBANA,ILLINOIS
NOTES ON SODIUM PRUSSJATE By LOUISS. POTSDAMER
Received February 3, 1919
Since t h e war has made us dependent upon our own resources it has become necessary t o foster many chemical industries. I n 1 9 1 7 t h e writer h a d t h e opportunity of studying and correcting t h e production of sodium prussiate from gas mass. T h e process presented below is new primarily in t h e following parts: 1--Recovery of tar and sulfur 2--Separate treatment of fine and coarse material 3--Direct causticization T h e outline is presented for t h e benefit of those who have not had these thoughts presented t o them and a s a suggestion for further experimental work. When t h e German supply of prussiate was cut off f r o m t h e manufacturers of blues they were forced t o look t o t h e local markets. T h e supply in t h a t field was very limited and measures were a t once t a k e n t o assist t h e blue manufacturers. Some gas plants had already begun t h e manufacture of sodium prussiate, and those which had not and h a d no intention of entering t h a t field were only too glad t o cooperate with t h e color makers by supplying gas mass. This latter material, which for years had been a drug on t h e market, h a d a t last come into its own. A material heretofore fit for t h e d u m p heaps had suddenly risen f r o m $5.00 t o $10.00 per t o n , dependent upon location. It was therefore only natural t h a t t h e gas producer:; should cooperate with t h e color makers, and t h a t t h e sodium prussiate market should boom. Gas mass, composed of hydrated iron oxide so spread through m7ood chips as t o allow of t h e free passage of gas in scrubbers, accumulates various chemicals, of which t h e following is a fairly representative list: Tar Ammonium salts Ferro- and ferricyanides Sulfur Double ammonium cyanides Sulfocyanides T h e problem before t h e manufacturer is t h e separation of these chemicals on a paying basis. The following is a brief report of t h e recovery processes: RECOVERY
OF TAR AND SULFUR
I n all manufacturing processes it is necessary t o have s minimum waste, and for this reason it is necessary t o remove t a r . T h e removal of sulfur gives t h e prussiate manufacturer a by-product of value. If t h e t a r is allowed t o remain in t h e mass it will cause t h e mass t o “ball” in a later lixiviating process. Un-
’
7 69
der t h e original methods of prussiate recovery t h e sulfur ocntained in t h e mass caused a loss due t o t h e formation of sulfocyanides from t h e ferrocyanides. T a r a n d sulfur may be removed in one operation b y extraction with a sulfur solvent such as carbon bisulfide. T h e details of t h e operation are simple and t h e time element is of small consequence if t h e operation is one of a battery. As a result of careful control t h e sulfur and t a r are dissolved in hot carbon disulfide and stored for recovery from t h e solvent a t leisure. When t h e final extraction is made, t h e remaining solvent is driven off by blowing t h e extractor with live steam. T h e desulfurized mass remaining in t h e extractor is of such nature t h a t i t would be difficult t o extract with water unless separated into fine and coarse material. This may be done by any of t h e standard methods. REMOVAL
OF
WATER-SOLUBLE
SULFOCYANIDES
AND
AMMONIUM S A L T S
I n t h e separation mentioned above t h e fine material will contain about t h e same percentage of prussiate as will t h e coarse material. T h e extraction of “fines” is hastened by s t e a m boiling with water. T h e usual countercurrent operation can be used here t o good advantage, remembering t h a t after each successive boiling t h e material must be allowed t o deposit from t h e solution. The liquors obtained here may, in t u r n , be used for t h e extraction of t h e “coarse” material. T h e extraction of “coarse” is less hasty in t h a t the, washes are made a t about 24-hr. intervals, t h e water being run on from below into false bottom tanks. T h e wash is drawn off, and may be added with t h e washes obtained from t h e “fines.” These washes contain t h e ammonium and sulfocyanide salts, from which t h e ammonia may be obtained by causticization and distillation. T h e a m monia which is driven off may be caught in distilled water and is t h e n ready for market. T h e remaining sulfocyanide liquors are of value to t h e producer if they contain over z per cent sulfocyanide salts, in which case they are concentrated and recovered. E X T R A C T I O N OF S O D I U X P R U S S I A T E
There are two good methods for extracting prussiate from “fines” and “coarse,” namely, ( a ) By hydrated lime ( b ) By causticization ( a ) The hydrated lime method is t h e older, a n d either fresh or commercial hydrated lime may be used. T h e material is thoroughly mixed with t h e lime a n d allowed t o s t a n d in open bins for several days. It is then carried t o tanks where t h e calcium salts are extracted, which salts form as a result of t h e reaction of t h e lime with t h e mass together with its resultant heat’ of reaction. Following t h e water extraction t h e solutions are treated with soda ash t o precipitate t h e
